In U.S. Pat. Nos. 4,015,341 and 4,347,670 are disclosed apparatus for drying seeds and other grains using microwave energy. Among the seeds specifically mentioned in these patents are soybeans which are an important oilseed crop. These apparatus can be used in the present process and the apparatus of U.S. Pat. No. 4,347,670 is specifically useful in this process.
In processing soybeans into high-protein soybean meal, the outer layer of the bean is removed before the oil is extracted from the beans. Removal of the outer layer of the soybean traditionally is done by passing the beans through cracking rolls to fracture the hulls and an aspirator is then used to separate the hulls from the cotyledons in the crushed soybeans.
Before crushing the soybeans, the beans are dried to remove about 1 to 3% of the moisture remaining in the beans and the dried beans are stored for about three to eight days to equalize the moisture content in the beans so that the hulls crack uniformly when passed through the cracking rolls. This storage time is commonly called the "tempering" period.
The tempering period is quite expensive because it adds to the overall processing time. It also requires extensive storage facilities which further adds to the expense of the present process.
The drying of the beans presently is done by any of several conventional drying processes, such as heated air passed over a moving conveyor containing the beans, etc. All of the known conventional drying processes require the tempering period.
U.S. Pat. No. 4,340,611 discloses a process by which the tempering procedure is eliminated by drying the beans in a microwave dryer of the types described in U.S. Pat. Nos. 4,015,341 and 4,347,670 and immediately cracking the hulls of the hot beans. This patent, however, does not discuss subsequent processing of the soybean meats.
After the hulls are cracked, they must be removed and separated from the meat in order to produce the desirable high-protein, low-fiber stream of meats. The separated meats then are flaked at a temperature generally around 160.degree. F. before being treated at a solvent extraction station to remove the oil. It is this latter portion of the soybean treatment process, i.e., the separation of meats from hulls and flaking, which the present invention primarily addresses.
A final step in the overall process is the production of soybean meal. The meal is produced after the oil has been removed from the meats and the resulting de-fatted meats have been desolventized and toasted.
High-protein, low-fiber soybean meal sells for a premium of approximately 6% over low-protein, high-fiber meal. Furthermore a plant processing high-protein, low-fiber meal can produce approximately 20% more product with the same equipment because of the reduced bulk of material flowing through the extraction plant and other portions of the system. Thus, at sites where there is a market for high-protein meal there are significant economic advantages for producing the high-protein product.
The essential step in producing high-protein meal is separation of the soybean hulls from the soybean meats. The conventional process for doing this requires a complicated multiplicity of shaking-screen separators, air-stream sorters, cyclone separators and their attendant fans, rotary airlock valves and conveyors. This plethora of equipment requires much plant floor space. Furthermore, the conventional system was developed before energy costs accelerated and its design does not lend itself to energy economics.
After the beans are cracked, the meats are separated from the hulls and the meats are treated to produce hot, flaked, bean meats. Although the subsequent solvent extraction process is not part of this invention, it is of primary importance to the overall economics of the plant that the flakes leaving this stage of the process and entering the solvent extraction stage be at the optimum conditions of temperature, moisture content and thickness.
Conventionally beans are cracked and the meats and hulls separated at a temperature of about 80.degree. F. Thereafter, before the beans are flaked, they must be heated to 160.degree. F. in a bean conditioner. Because we crack hot beans, we are able to eliminate the bean conditioner, reduce the number of fines produced in the cracking rolls, eliminate a primary separation step because of the fewer fines in the cracked product, and we also recover waste heat from the magnetrons, if the product conditioner is a microwave dryer. All of the foregoing reduces process equipment cost, needed plant space, conveying equipment, and utilizes less energy.
The present invention comprises a system for conditioning oilseeds in a fast efficient manner, utilizing hot seeds from cracking through flaking, with subsequent savings in equipment cost and plant space, as well as reducing energy requirements and producing a high-protein, low-fiber product of reduced fines content.